Fork loader with lift-controlled enclosure

ABSTRACT

A fork loader has a wire-net enclosure giving access to a lifting fork when the latter is in its normal, unloaded state. A clevis articulated to the head of the fork, at an acute angle to the axis of a pneumatic cylinder rigid with the fork, acts through a plunger upon an air cushion in the cylinder when the clevis is lifted by a crane while the fork is weighted down by a load. The free end of the plunger thereupon releases a sickleshaped arm on the pivotal shaft of a swingable front part of the enclosure whereby that part is allowed to drop down in front of the pallet, being subsequently locked in place by a pair of pins released from a withdrawn position by a further advance of the plunger into engagement with a spring-loaded camming lever.

United States Patent Primary Examiner-Andres H. Nielsen Att0rney-l(arlF. Ross ABSTRACT: A fork loader has a wire-net enclosure giving accessto a lifting fork when the latter is in its normal, unloaded state. Aclevis articulated to the head of the fork, at an acute angle to theaxis of a pneumatic cylinder rigid with the fork, acts through a plungerupon an air cushion in the cylinder when the clevis is lifted by a cranewhile the fork is weighted down by a load. The free end of the plungerthereupon releases a sickle-shaped arm on the pivotal shaft of aswingable front part of the enclosure whereby that part is allowed todrop down in front of the pallet, being subsequently locked in place bya pair of pins released from a withdrawn position by a further advanceof the plunger into engagement with a springloaded camming lever.

52 57 57 87 1 5/ j a: I x l n O I I I 60 V/ "'PATENIEU M R 30 ml SHEET 1BF 2 INVENTOR.

VIKTOR ZUPANCIC SS (QM 6RD Attorney FORK LOADER WITH LIFT-CONTROLLEDENCLOSURE My present invention relates to a fork loader of the typewherein a lifting fork has a pair of depending prongs terminating ingenerally horizontal tines designed to engage a. load such as a palletused for the transportation of goods.

The general object of my invention is to provide means for automaticallylowering an enclosure, such as a wire-net cage, around the load when thelatter is being gripped by the fork for hoisting with the aid of acrane.

This object is realized, pursuant to the present invention, with theaidof a connecting member, specifically a plunger guided in a pneumaticcylinder, which is movably secured to the head portion of the fork andis biased into a normal position from which it can be displaced into anoff-normal position, against the force of the biasing means representedby an air cushion in the cylinder, upon the exertion of a lifting forceon aghoisting means such as a clevis engaging this connecting member; amobile front part of an enclosure such as a wire cage,v normallyretracted to give access to'the load-engaging -.prongs of the fork, islinked with'a transmission element, such as a curved camming arm, whichis engageable by the connecting member in its normal position to holdthe front part of the cage retracted while enablingthis-part to descendforwardly of the load upon the lifting of the weighted fork by theaforementioned hoisting means.

According to another feature of my invention, the fork is providedwithdetent means suchas a, pair of locking pins normally held in awithdrawn position provided with actuating means, such as a camminglever, engageable by'the connecting member upon the disengagementthereof from the transmission element for the mobile cage part toreleasethe detent means in order to latch that part in a swung-downposition.

The above and other features of my invention will be described ingreater detail hereinafter with reference to the accompanying drawing inwhich:

FIG. I is an axonometric view of a loading device embodying myinvention, shown in an unloaded position .with the front part of itsprotective cage upwardly retracted;

FIG. 2 is a longitudinal sectional view of the head portion of a liftingfork forming part of the device of FIG. I,.together with associatedelements;

FIG. 3 is a view similar to FIG. 2 but showing the pans in a differentrelative position;

FIG. 4 is a top view of the assembly of FIGS. 2 and 3 shown partly insection on the line IV-IV of FIG. 2;

FIG. 5 is a side-elevational view, with parts broken away, of a modifiedlifting fork adapted to be used in the device of FIG. I; and

FIG. 6 is an axonometric view of a detail shown within'the circle VI ofFIG. I.

The device illustrated in FIG. 1 comprises, essentially, a lifting forkwith a head portion 50- having a pair of divergent prongs 51 dependingtherefrom, these prongs terminating in two short parallel legs- 52 fromwhich tines '53 extend forwardly for engagement with a loading palletnot shown. The legs 52 of the fork are interconnected by a'brace 54, asimilar brace 55 extending across the upper portions of the prongs 51.Two handles 62 and 63 are respectively secured to these .bracesJ-Ieadportion 50, which interconnects the upper ends 61 of the prongs SI in amanner more fully described hereinafter, is engaged by a clevis 74,forming part of a hoisting mechanism, through the intermediary of aconnecting member 13 (FIGS. 2-4) constituted by the rod of a plungerwhose head 11 is received in a cylinder 1 rigid with fork-portion 50.Clevis 74is suspended via a steel cable 75 from a ring 76 adapted to'beengaged by a lifting device such as a crane Cage portion 82 has a cutout84 clearing the cable 75 in its upwardly retracted position shown infull lines in FIG. I. The two relatively movable cage portions 8i, 82have frames BI, 83 interlinked with the wire netting thereof.

The connection between the fork 50-53 and the rear part 81 of the cageincludes, in addition to the tubes 57, a pair of tubes 56 extendinglaterally outwardly from the legs 52 in line with the brace 54 andterminating in a pair of cheek plates 44 (FIG. 6), the frame 81 of cageportion 81 being gripped by hooked straps 46 secured to these cheekplates by bolts 45. Also supported on plates 44 are a pair of lockingpins 43 biased outwardly by springs 42 within tubular housings 41, theinner ends of the pins 43 being connected to respective tension cables36 which pass around rollers 37 toward the head portion 50 of the fork.The upper ends of cables 36 are secured to a pair of arms 35 whose otherextremities are rigid with a shaft 3|, FIGS. 24, which is pivotallymounted in head portion 50 and also carries a camming lever 32 urged bya spring 34 into a position in which the arms 35 tension the cables 36to hold the pins 43 withdrawn againstthe force of their loading springs42. The lower rear comers of the three-sided cage portion 81 formsseats'87 engageable by the pins 43 upon a slackening of cables 36 asmore fully described hereinafter. Angle plates 85 at the upper rearcorners of this cage portion are secured to the projecting ends ofpivotal shaft 57 by connecting tabs 85. As seen in FIGS. 2 and 3, shaft57' is offset fromthe axis of cylinder 1, i.e., from the direction ofmovement of plunger 13.

As best seen in FIGS. 2 and 3, shaft57' carries a cam 59 in the form ofa sickle-shaped arm having a hub 58 clamped onto said shaft. Plunger I3is connected through a cross-pin IS with a pair of side bars 27whose'rear ends are interconnected bya .pin 28 supporting a deflectingroller 29. An air cushion 6 in cylinder I bears upon a piston 2 freelymovable within that cylinder, this piston in turn acting through an oilcolumn 14 upon the head 11 of plunger 13. With the plunger 13 unstressedby the clevis 74 as illustrated in FIG. 2, the pressure of air cushion 6tends to maintain the roller 29 in contact with arm 59.

The ends of cylinder I are sealed by plugs 7 and 9, the latter beingtraversed by the rod 13 while the former is provided with an air inletin a valve in a nose 8. Piston 2 comprises a pair of discs 3interconnected by a mounting bolt 4 and serving to hold a pair ofpacking rings 5 in position. A similar packing ring 12 is provided onthe circumference of plunger head 11.

The head portion 15 of the lifting fork comprises a pair of angle ironsI6'which are interconnected by a tie 17 and are secured to a pair ofplates 18 supporting and secured to the overlying ends 6l of prongs 51as best seen in FIG. I. Brackets 16 are also fastened to a pair of sidewings 21 formed with slots 22 which accommodate two pairs of rollers 24,26 mounted via studs 23, 25 on the arms 27 of plunger 13. Studs 23 alsoserve as pivots for two pairs of straps 71, 72 which are interconnectedby a cross-pin 73 and secured to the lower ends of the arms of clevis74. A bracket 33, projecting from one of the arms 27, serves as asupport for spring 34.

I shall now-describe the operation of the system illustrated in FIGS.I-4 and 6.

In the normal position illustrated in FIG. 2, air cushion 6 is expandedso that piston 2 and, with it, head II of plunger 13 are maintained intheir extreme left-hand positions in which the roller 29 at the free endof plunger 13 bears upon the curved arm 59 to hold the cage portion 82retracted as illustrated in full lines in FIG. I. In this position, thetines 53 of the lifting fork are accessible for engagement with aloading pal let. When the fork is thus weighted down by the load, withits nose 8 pointing upwardly as illustrated in FIG. I, an upward pullupon ring 76 by a lifting crane exerts upon clevis '7 a force in thedirection of arrow C, FIG. 3, i.e. at an acute angle to the axis ofcylinder I. As a result, a component of the lifting force represented byarrow C acts upon plunger 13 in a sense urging it into cylinder I tocompress the air cushion 6 therein,

with concurrent withdrawal of roller 29 from arm 59 whereby the latteris free to swing clockwise (arrow A, FIG. 2) as the mobile cage portion82 drops down under its own weight in front of the load to occupy theposition illustrated in phantom lines in FIG. 1. In this position theseats 87 are aligned with the locking pins 43 which, however, remainretracted until a further inward motion of plunger 13 (to the right inFIG. 3) causes the roller 28 to depress the camming lever 32 against theforce of spring 33, thereby slackening the tension cables 36 (arrow B,FIG. 2) sufficiently to let the locking pins 43 enter the seats 87 forlatching the front portion 82 onto the rear portion 81 of cage 80. Thedevice of FIG. 1 can now be raised and transported to any desiredlocation where it is set down to relieve the force of gravity actingupon the fork 50- -53 so that the energy stored in air cushion 6 can nowreturn the plunger 13 to its original position; as the roller 28 clearsthe camming lever 32, spring 34 withdraws the locking pins 43 whereuponthe front portion 82 of cage 80 can be raised either manually or by thepressure of roller 28 upon arm 58 to restore the original position.

with the loading device freely suspended from the crane by the ring 76,the direction represented by arrow C is of course vertical. The centerof gravity of the load is then vertically aligned with the suspensionpoint represented by the axis of studs 23, as will be well understood.The initial angle between the clevis 74 and the axis of cylinder 1,shown in FIG. 3, is determined by the forward divergence of that axisfrom the tines 53 as seen in FIG. 1 (cf. also FIG. As the plunger 13advances from its normal position (FIG. 2) past the intermediateposition of FIG. 2 to its working position in which the roller 29deflects the camming lever 32, the suspension point moves forwardly withreference to the center of gravity of the load.

In FIG. 5 I have shown a modified fork structure in which a fluidchamber 53' lies in the plane of symmetry of the tines 53, one of whichis shown partly broken away in the FIG. Blockshaped clamping elements53" project laterally outwardly toward these tines for grippingengagement with a load. Such an engagement is brought about by thepressure of a hydraulic fluid delivered to chamber 53' through an inlet99 by a conduit 98 which opens at 97 into a hydraulic cylinder 96 havinga piston 95 on a rod 94. A clevis 92 is connected via straps 91 with across-pin 93 secured to the free end of piston rod 94 while the cylinder96 is connected with the head portion 50 of the fork, secured as beforeto the upper ends 61 of prongs 51, through the intermediary of links 71.Thus, the exertion of an upward force C upon clevis 92, aside fromraising the fork head to bring about the aforedescribed swing of cageportion 82, also actuates the clamping means 53".

Iclaim:

I. A loading device comprising a fork with a pair of load-engagingprongs depending from a common head portion provided with elongate guidemeans; a connecting member movably secured to said head portion by saidguide means; biasing means tending to maintain said connecting member ina normal position relative to said head portion; hoisting means engagingsaid connecting member at an acute angle to said guide means for urgingsame into an off-normal position, against the force of said biasingmeans, upon upward movement of said hoisting means with reference tosaid prongs weighted down by an engaged load; an enclosure for said loadincluding a mobile front part adapted to give access to said load in anupwardly retracted position; and transmission means linked with saidfront part and engageable by said connecting member in said normalposition thereof for normally holding saidfront part in said retractedposition while enabling said front part to descend forwardly of the loadupon a lifting of the weighted fork by said hoisting means.

2. A device as defined in claim I wherein said guide means comprises acylinder, said connecting member being a plunger received in saidcylinder, said biasing means including an air cushion in said cylinder.

3. A device as defined in claim 2 wherein said plunger has a free endprovided with a roller, said transmission means including a pivotalshaft for said front part offset from the direction of movement of saidplunger and a cam on said shaft normally in contact with said roller.

4. A device as defined in claim 2 wherein said prongs terminate in apair of fortines diverging forwardly from the axis of said cylinderwhereby the latter is upwardly inclined in a horizontal position of saidtines.

5. A device as defined in claim I, further comprising detent means onsaid fork for latching said front part in its lowered position, andspring-loaded actuating means for said detent means normally holdingsame in a withdrawn position, said actuating means being positioned forengagement by said connecting member subsequently to disengagementthereof from said transmission means for releasing said detent meansfrom said withdrawn position.

6. A device as defined in claim 1 wherein said hoisting means includes ahydraulic cylinder and piston movable relatively to each other togenerate hydraulic pressure upon the exertion of an upward force to asuspension point of said hoisting means, said fork being provided withhydraulic clamping means juxtaposed with said prongs for gripping a loadin response to said hydraulic pressure.

7. A loading device comprising a fork with a pair of load-engagingprongs depending from a common head portion; a connecting member movablysecured to said head portion; biasing means tending to maintain saidconnecting member in a normal position relative to said head portion;hoisting means engaging said connecting member for urging same into anoffnormal position, against the force of said biasing means, upon upwardmovement of said hoisting means with reference to said prongs weighteddown by an engaged load; an enclosure for said load including a mobilefront part adapted to give access to said load in an upwardly retractedposition; and transmission means linked with said front part andengageable by said connecting member in said normal position thereof fornormally holding said front part in said retracted position whileenabling said front part to descend forwardly of the load upon a liftingof the weighted fork by said hoisting means; said hoisting meansincluding a hydraulic cylinder and piston movable relatively to eachother to generate hydraulic pressure upon the exertion of an upwardforce to a suspension point of said hoisting means, said fork beingprovided with hydraulic clamping means juxtaposed with said prongs forgripping a load in response to said hydraulic pressure.

8. A device as defined in claim 7 wherein said head portion is providedwith elongate guide means for said connecting member, said hoistingmeans being coupled with said connecting member at an acute angle tosaid guide means.

9. A loading device comprising a fork with a pair of load-engagingprongs depending from a common head portion; a connecting member movablysecured to said head portion; biasing means tending to maintain saidconnecting member in a normal position relative to said head portion;hoisting means engaging said connecting member for urging same into anoffnorrnal position, against the force of said biasing means, uponupward movement of said hoisting means with reference to said prongsweighted down by an engaged load; an enclosure for said load including amobile front part adapted to give access to said load in an upwardlyretracted position; transmission means linked with said front part andengageable by said connecting member in said normal position thereof fornormally holding said front part in said retracted position whileenabling said front part to descend forwardly of the load upon a liftingof the weighted fork by said hoisting means; detent means on said forkfor latching said front part in its lowered position; and spring-loadedactuating means for said detent means normally holding same in awithdrawn position, said actuating means being positioned for engagementby said connecting member subsequently to disengagement thereof fromsaid transmission means for releasing said detent means from saidwithdrawn position.

10, A device as defined in claim 9 wherein said enclosure furtherincludes a rear part fixed with reference to said fork, said detentmeans comprising a pair of spring-biased locking pins mounted onopposite sides of'said rear part for engagement with corresponding sidesof said front part.

11. A device as defined in claim 10 wherein said actuating meanscomprises a spring-loaded camming lever and flexible link meansconnecting said levelwith said pins, said transmission means including apivotal shaft for said front part and a cam on said shaft, saidconnecting member being provided with a deflecting roller normally incontact with said cam and positioned to engage said camming lever upondisengaging said cam to facilitate a downward swing of said front part.

12. A device as defined in claim 11 wherein said connecting membercomprises a plunger, said biasing means including a pneumatic cylinderon said head portion receiving said plunger, said head portion beingprovided with slotted lateral wings, said plunger carrying saiddeflecting roller on a free end thereof and being further provided withlateral roller means received in slots of said wings.

1. A loading device comprising a fork with a pair of loadengaging prongsdepending from a common head portion provided with elongate guide means;a connecting member movably secured to said head portion by said guidemeans; biasing means tending to maintain said connecting member in anormal position relative to said head portion; hoisting means engagingsaid connecting member at an acute angle to said guide means for urgingsame into an off-normal position, against the force of said biasingmeans, upon upward movement of said hoisting means with reference tosaid prongs weighted down by an engaged load; an enclosure for said loadincluding a mobile front part adapted to give access to said load in anupwardly retracted position; and transmission means linked with saidfront part and engageable by said connecting member in said normalposition thereof for normally holding said front part in said retractedposition while enabling said front part to descend forwardly of the loadupon a lifting of the weighted fork by said hoisting means.
 2. A deviceas defined in claim 1 wherein said guide means comprises a cylinder,said connecting member being a plunger received in said cylinder, saidbiasing means including an air cushion in said cylinder.
 3. A device asdefined in claim 2 wherein said plunger has a free end provided with aroller, said transmission means including a pivotal shaft for said frontpart offset from the direction of movement of said plunger and a cam onsaid shaft normally in contact with said roller.
 4. A device as definedin claim 2 wherein said prongs terminate in a pair of fortines divergingforwardly from the axis of said cylinder whereby the latter is upwardlyinclined in a horizontal position of said tines.
 5. A device as definedin claim 1, further comprising detent means on said fork for latchingsaid front part in its lowered position, and spring-loaded actuatingmeans for said detent means normally holding same in a withdrawnposition, said actuating means being positioned for engagement by saidconnecting member subsequently to disengagement thereof from saidtransmission means for releasing said detent means from said withdrawnposition.
 6. A device as defined in claim 1 wherein said hoisting meansincludes a hydraulic cylinder and piston movable relatively to eachother to generate hydraulic pressure upon the exertion of an upwardforce to a suspension point of said hoisting means, said fork beingprovided with hydraulic clamping means juxtaposed with said prongs forgripping a load in response to said hydraulic pressure.
 7. A loadingdevice comprising a fork with a pair of load-engaging prongs dependingfrom a common head portion; a connecting member movably secured to saidhead portion; biasing means tending to maintain said connecting memberin a normal position relative to said head portion; hoisting meansengaging said connecting member for urging same into an off-normalposition, against the force of said biasing means, upon upward movementof said hoisting means with reference to said prongs weighted down by anengaged load; an enclosure for said load including a mobile front partadapted to give access to said load in an upwardly retracted position;and transmission means linked with said front part and engageable bysaid connecting member in said normal position thereof for normallyholding said front part in said retracted position while enabling saidFront part to descend forwardly of the load upon a lifting of theweighted fork by said hoisting means; said hoisting means including ahydraulic cylinder and piston movable relatively to each other togenerate hydraulic pressure upon the exertion of an upward force to asuspension point of said hoisting means, said fork being provided withhydraulic clamping means juxtaposed with said prongs for gripping a loadin response to said hydraulic pressure.
 8. A device as defined in claim7 wherein said head portion is provided with elongate guide means forsaid connecting member, said hoisting means being coupled with saidconnecting member at an acute angle to said guide means.
 9. A loadingdevice comprising a fork with a pair of load-engaging prongs dependingfrom a common head portion; a connecting member movably secured to saidhead portion; biasing means tending to maintain said connecting memberin a normal position relative to said head portion; hoisting meansengaging said connecting member for urging same into an off-normalposition, against the force of said biasing means, upon upward movementof said hoisting means with reference to said prongs weighted down by anengaged load; an enclosure for said load including a mobile front partadapted to give access to said load in an upwardly retracted position;transmission means linked with said front part and engageable by saidconnecting member in said normal position thereof for normally holdingsaid front part in said retracted position while enabling said frontpart to descend forwardly of the load upon a lifting of the weightedfork by said hoisting means; detent means on said fork for latching saidfront part in its lowered position; and spring-loaded actuating meansfor said detent means normally holding same in a withdrawn position,said actuating means being positioned for engagement by said connectingmember subsequently to disengagement thereof from said transmissionmeans for releasing said detent means from said withdrawn position. 10.A device as defined in claim 9 wherein said enclosure further includes arear part fixed with reference to said fork, said detent meanscomprising a pair of spring-biased locking pins mounted on oppositesides of said rear part for engagement with corresponding sides of saidfront part.
 11. A device as defined in claim 10 wherein said actuatingmeans comprises a spring-loaded camming lever and flexible link meansconnecting said lever with said pins, said transmission means includinga pivotal shaft for said front part and a cam on said shaft, saidconnecting member being provided with a deflecting roller normally incontact with said cam and positioned to engage said camming lever upondisengaging said cam to facilitate a downward swing of said front part.12. A device as defined in claim 11 wherein said connecting membercomprises a plunger, said biasing means including a pneumatic cylinderon said head portion receiving said plunger, said head portion beingprovided with slotted lateral wings, said plunger carrying saiddeflecting roller on a free end thereof and being further provided withlateral roller means received in slots of said wings.